ATC provides IFR aircraft separation
services for NAS users. Since the
capabilities of IFR operators vary
from airlines operating hundreds of
complex jet aircraft to private pilots
in single engine, piston-powered airplanes,
the ATC system must accommodate
the least sophisticated user.
The lowest common denominator is
the individual controller speaking to
a single pilot on a VHF voice radio
channel. While this commonality is
desirable, it has led to a mindset
where other opportunities to interact
with NAS users have gone undeveloped.
The greatest numbers of operations
at the 20 busiest air carrier
airports are commercial operators (airlines and commuters)
operating IFR with some form of ground-based
operational control. Since not all IFR operations have
ground-based operational control, very little effort has
been expended in developing ATC and Airline Operations
Control Center (AOC) collaboration techniques, even
though ground-based computer-to-computer links can
provide great data transfer capacity. Until the relatively
recent concept of Air Traffic Control-Traffic Flow
Management (ATC-TFM), the primary purpose of ATC
was aircraft separation, and the direct pilot-controller
interaction was adequate to the task. Effective and efficient
traffic flow management now requires a new level of
control that includes the interaction of and information
transfer among ATC, TFM, AOCs, and the cockpit.
[Figure 1-17]

As the first step in modernizing the traffic flow management
infrastructure, the FAA began reengineering
traffic flow management software using commercial
off-the-shelf products. In FY 1996, the FAA and
NASA collaborated on new traffic flow management
research and development efforts for the development
of collaborative decision making tools that will enable
FAA traffic flow managers to work cooperatively with
airline personnel in responding to congested conditions.
Additionally, the FAA provided a flight scheduling
software system to nine airlines.

LAND AND HOLD SHORT OPERATIONS

Many older airports, including some of the most congested,
have intersecting runways. Expanding the use
of Land and Hold Short Operations (LAHSO) on
intersecting runways is one of the ways to increase the
number of arrivals and departures. Currently, LAHSO operations are permitted only on dry runways under
acceptable weather conditions and limited to airports
where a clearance depends on what is happening on
the other runway, or where approved rejected landing
procedures are in place. A dependent procedure example
is when a landing airplane is a minimum distance
from the threshold and an airplane is departing an
intersecting runway, the LAHSO clearance can be
issued because even in the event of a rejected landing,
separation is assured. It is always the pilotís option to
reject a LAHSO clearance.

Working with ICAO, pilot organizations, and industry
groups, the FAA is developing new LAHSO procedures
that will provide increased efficiency while maintaining
safety. These procedures will address issues such as wet
runway conditions, mixed commercial and general aviation
operations, the frequency of missed approaches, and
multi-stop runway locations. After evaluating the new
procedures using independent case studies, the revised
independent LAHSO procedures may be implemented in
the near future.

SURFACE MOVEMENT GUIDANCE AND CONTROL SYSTEM

To enhance taxiing capabilities in low visibility conditions
and reduce the potential for runway incursions,
improvements have been made in signage, lighting, and
markings. In addition to these improvements, airports
have implemented the Surface Movement Guidance and
Control System (SMGCS),4 a strategy that requires a low
visibility taxi plan for any airport with takeoff or landing
operations with less than 1,200 feet RVR visibility conditions.
This plan affects both aircrew and airport vehicle
operators, as it specifically designates taxi routes to and
from the SMGCS runways and displays them on a
SMGCS Low Visibility Taxi Route chart.

SMGCS is an increasingly important element in a seamless,
overall gate-to-gate management concept to ensure
safe, efficient air traffic operations. It is the ground-complement
for arrival and departure management and the
en route components of free flight. The FAA has supported
several major research and development efforts
on SMGCS to develop solutions and prototype systems
that support pilots and ATC in their control of aircraft
ground operations.